Polyandry exists in extreme environments. It’s one of three forms of human marriage i.e monogamy (the human norm), polygyny, and polyandry.
This system will probably exist in China in another generation—what with the one child policy and such a high rate of either aborting female children, killing them after birth, or sending them off to be adopted elsewhere. There is already an abundance of boys—when they become men they will have to share their wives.